diff --git a/codex-rs/core-plugins/src/loader_tests.rs b/codex-rs/core-plugins/src/loader_tests.rs
index 897c840432..7711261ac6 100644
--- a/codex-rs/core-plugins/src/loader_tests.rs
+++ b/codex-rs/core-plugins/src/loader_tests.rs
@@ -116,7 +116,7 @@ async fn agent_plugin_codex_mcp_overlay_only_forwards_matching_stdio_server_env_
 }
 
 #[tokio::test]
-async fn agent_plugin_codex_mcp_overlay_supports_inline_legacy_servers() {
+async fn agent_plugin_codex_mcp_overlay_supports_inline_legacy_servers_without_portable_env() {
     let temp_dir = TempDir::new().expect("tempdir");
     let plugin_root = temp_dir.path().join("plugin");
     write_file(
@@ -130,8 +130,7 @@ async fn agent_plugin_codex_mcp_overlay_supports_inline_legacy_servers() {
   "mcpServers": {
     "shared": {
       "type": "stdio",
-      "command": "portable-server",
-      "env": {"TOKEN": "${TOKEN}"}
+      "command": "portable-server"
     }
   }
 }"#,
@@ -139,13 +138,12 @@ async fn agent_plugin_codex_mcp_overlay_supports_inline_legacy_servers() {
 
     let mut expected = load_plugin_mcp_servers(&plugin_root, /*auth_mode*/ None).await;
     let Some(McpServerConfig {
-        transport: McpServerTransportConfig::Stdio { env, env_vars, .. },
+        transport: McpServerTransportConfig::Stdio { env_vars, .. },
         ..
     }) = expected.get_mut("shared")
     else {
         panic!("expected portable stdio server");
     };
-    env.as_mut().expect("portable environment").remove("TOKEN");
     env_vars.push("TOKEN".into());
 
     write_file(
diff --git a/codex-rs/core/tests/suite/plugins.rs b/codex-rs/core/tests/suite/plugins.rs
index 04b502888b..2e33888a3a 100644
--- a/codex-rs/core/tests/suite/plugins.rs
+++ b/codex-rs/core/tests/suite/plugins.rs
@@ -716,7 +716,7 @@ async fn agent_plugin_root_mcp_stdio_tool_round_trip_expands_reserved_paths_and_
                     overlay_call_id,
                     "mcp__agent",
                     "echo",
-                    r#"{"message":"ping","env_var":"PATH"}"#,
+                    r#"{"message":"ping","env_var":"INSTA_WORKSPACE_ROOT"}"#,
                 ),
                 ev_completed("resp-3"),
             ]),
@@ -748,10 +748,7 @@ async fn agent_plugin_root_mcp_stdio_tool_round_trip_expands_reserved_paths_and_
             "agent": {
                 "type": "stdio",
                 "command": format!("./{stdio_server_name}"),
-                "env": {
-                    "MCP_TEST_VALUE": "${PLUGIN_ROOT}|${PLUGIN_DATA}",
-                    "PATH": "${PATH}"
-                }
+                "env": {"MCP_TEST_VALUE": "${PLUGIN_ROOT}|${PLUGIN_DATA}"}
             }
         }
     });
@@ -762,7 +759,7 @@ async fn agent_plugin_root_mcp_stdio_tool_round_trip_expands_reserved_paths_and_
     std::fs::create_dir_all(plugin_root.join(".codex-plugin"))?;
     std::fs::write(
         plugin_root.join(".codex-plugin/plugin.json"),
-        r#"{"name":"acme.tools","mcpServers":{"agent":{"command":"ignored","env_vars":["PATH"]}}}"#,
+        r#"{"name":"acme.tools","mcpServers":{"agent":{"command":"ignored","env_vars":["INSTA_WORKSPACE_ROOT"]}}}"#,
     )?;
     let mut builder = test_codex().with_home(Arc::clone(&codex_home));
     let test_codex = builder.build_with_remote_and_local_env(&server).await?;
@@ -824,7 +821,7 @@ async fn agent_plugin_root_mcp_stdio_tool_round_trip_expands_reserved_paths_and_
             .as_ref()
             .and_then(|content| content.get("env"))
             .and_then(serde_json::Value::as_str),
-        Some(std::env::var("PATH")?.as_str())
+        Some(std::env::var("INSTA_WORKSPACE_ROOT")?.as_str())
     );
     let requests = mock.requests();
     let search_output = requests[1].tool_search_output(search_call_id);